A high-quality GaSe single crystal was grown by the Bridgman method. The X-ray rocking curve for the studied GaSe sample is symmetric and the Full Width at Half Maximum (FWHM) is only 46 arcs, which is the smallest value ever reported for GaSe crystals. The IR-transmittance is about 66% in the range from 500 to 4000 cm⁻¹. The photoluminescence spectrum at 9.2 K shows a symmetric and sharp excition peak in 2.1046 eV. The results indicate that the as-grown GaSe crystal is of high crystalline quality. The as-grown $\mathsf{\epsilon }$ -GaSe crystal has a p-type conductance with the resistivity of 10³ Ω/cm, and the Hall mobility is ~25 cm² V⁻¹ s⁻¹. Few-layer GaSe crystals were prepared through mechanical exfoliation from this high-quality crystal sample. Few-layer GaSe-based photodetectors were fabricated, which exhibit an on/off ratio of 10⁴, a field-effect differential mobility of 0.4 cm² V⁻¹ s⁻¹, and have a fast response time less than 60 ms under light illumination.

A radiation damage mechanism of CdZnTe:In crystals under ⁶⁰Co γ-rays with a cumulated radiation dose of ~2.4 kGy was proposed and discussed. Thermally stimulated current (TSC) measurements were carried out to characterize the γ-ray induced radiation damage. Four main trap levels (T1–T4) originating at four main microscopic defective states were identified. We attributed traps T1 and T2 to shallow donor impurities and shallow acceptor A-centers, respectively. Trap T3 was ascribed to dislocations and a great increase in defect concentration occurred after radiation. Trap T4 originated at deep acceptor Cd vacancies and vacancy related defect complexes and a considerable increase in the trap density, after radiation, lead to the conversion of conduction type from n to p in the Hall measurements and a Fermi level shift in the temperature-dependent resistivity analyses. Radiation induced electrically active defects contributed to the variation of the electrical compensation conditions and the worsening of the charge transport properties, which were consequently reflected by a significant deterioration in CZT detector performance.

Herein, we study the crystallographic configuration of rosette-like dislocation clusters introduced by indentation in CdZnTe (CZT) crystal and the effects of the dislocations on the carrier transport process. The Vickers hardness test was used to generate dislocations artificially on the ( ) Te face of the CZT crystal at room temperature. Etch pit density (EPD) revealed by Everson etchant showed that the dislocation density increased from 4.9 × 10⁴ cm⁻² to a concentration too high to be evaluated after the indentation. A model was proposed to explain the rosette-like dislocation clusters. It was verified that the tetrahedron with small size and high EPD belonged to Te(g) dislocations on the ( ) Te face. The hexagon-like distribution of pile-ups formed during the indentation was determined by the zinc-blende structure of CZT, rather than the direction of the indenter. The dislocation pile-up during propagation was observed and analyzed based on the rule proposed by Lomer and Cottrell. The ion beam induced charge (IBIC) measurements showed low carrier collection efficiency (CCE) in the dislocation generation areas, which confirms that the dislocations and related defects can significantly degrade the CCE of a CZT detector. Measurements of low temperature photo-luminescence (PL) showed that the emission peak located at 1.485 eV highly increased in the indentation area and was responsible for the performance degradation of the detectors.

The effect of deep-level defects is a key issue for the applications of CdZnTe high-flux photon counting devices of X-ray irradiations. However, the major trap energy levels and their quantitive relationship with the device’s performance are not yet clearly understood. In this study, a 16-pixel CdZnTe X-ray photon counting detector with a non-uniform counting performance is investigated. The deep-level defect characteristics of each pixel region are analyzed by the current–voltage curves (I–V), infrared (IR) optical microscope photography, photoluminescence (PL) and thermally stimulated current (TSC) measurements, which indicate that the difference in counting performance is caused by the non-uniformly distributed deep-level defects in the CdZnTe crystals. Based on these results, we conclude that the CdZnTe detectors with a good photon counting performance should have a larger ${\mathrm{Te}}_{\mathrm{cd}}^{2+}$ and Cd vacancy-related defect concentration and a lower A-center and Te_i concentration. We consider the deep hole trap Te_i, with the activation energy of 0.638–0.642 eV, to be the key deep-level trap affecting the photon counting performance. In addition, a theoretical model of the native defect reaction is proposed to understand the underlying relationships of resistivity, deep-level defect characteristics and photon counting performance.